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Old 07-24-2008, 01:13 PM   #1 (permalink)
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Some suggestions and notes on the MPGuino

Hey all, dcb -

After using the MPGuino for a bit, I figured I'd throw my thoughts in there for you to think about. I figure I have a unique perspective since I've used both the guino and the superMID.

Anyweigh, I'll lay out each point and expand upon it a bit.

1. It rocks - I'd forgotten how much I liked having instantaneous mileage readouts. What's more, the big numbers are something great that the superMID never had.
2. LCD sucks - The big numbers help a lot, but the screen is still near impossible to see easily when it's bright outside. I know the idea is too keep it cheap, but could there not be an option for a nice green, backlight lcd that has the same sort of mechanics, even if it costs a bit more?
3. Bouncy numbers - Just driving along there will be quite a bit of bouncing around of the instantaneous numbers. Usually I'll get a constant alternation between something like 58 and 66 or something like that. Kinda distracting. It might be easy to smooth it out, or else it might be easy to add something like the SMID had, which was a mpg over last km function
4. Customizable screen - If there were an easy way to put the four functions you wanted on the same screen (such as instant, trip, pulse width, and speed) within the world of the unit itself, that'd be pretty damn sweet. The SMID never had this but it showed 16 things at once so it wasn't too necessary
5. The big thing, prefab - I realize it's a troublesome thing to try and prefab and sell an open source thing, but I talked to dozens of people about the mpguino at hybridfest that liked it but were scared off by the soldering. Making this thing more accessible would be worth the money for most people and would really grow the userbase, and I'm sure someone would figure something out, whether dcb wanted to do the selling himself, someone else wants to just to the work themselves, or there is some sort of prefab company that will do drop shipping. *shrug* But from my perspective as the one who wants to spread and make ecomodding accessible, this is really the most important task. After all, the more people we can get using it, the more people will be supporting dev and working on code and junk.
6. Oh! Another thing. How to I prevent it from reseting the tank info? Sometimes it'll even reset due to eoc...

ben

PS: I peaked at the code and couldn't see where there was any averaging done on the instantaneous figure. Could you point me to the line or is it not there at all?

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Old 07-24-2008, 04:16 PM   #2 (permalink)
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Not to put too fine a point on this issue, but if they are "afraid" of soldering, how do they have the desire to cut/splice it in to their vehicle and scare up the values to make it run accurately?

Yes, I agree that there should be a more shrink-wrap like solution. But, by it's very nature, it's a full on DIY - and can be done quite cheaply if you are so inclined. That kinda seems a bit contradictory. Also, the infrastructure to upload updates to the code, how would they get those?

Maybe it's a bit too soon for those ideas. Let's let it grow a bit and see where it goes.
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Old 07-24-2008, 07:07 PM   #3 (permalink)
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I think the pre-fab one is a write once affair except for the advanced users who know how to dissect it and put a new program on the chip. It would be nice if the scangauge let you do that, but I think they are too worried about pirating to make the hex file available for public download. The installation might seem less intimidating, like installing a tachometer vs building then installing a tach. It would get into more cars that way. But I'm willing to agree that it is still a tad early. If I can get a batch of PCBs sorted out, that would be a good start.

Let me go point by point with Bens comments, I think we are on the same page here.

1. Gracias, I hope it helped your record tank (very nice numbers there). I assume you were happy with Yoshi's initial vx figure?

2. BLUE LCD sucks, yup. I added a link to this guy in post 1. I've got a few, was hoping to order a few PCBs to try them out. NHD-0216K1Z-FL-YBW

3. That has been on the todo list for a while. I'll bump it up a notch. I need to get off timer(0) and on to timer(2) with my own ISR first.

4. The screens just kind of happened I don't know if there will be enough program space left once the "important" updates get made to have a fully user definable screen. And with this little real estate it will always be a compromise. It isn't what you were asking for, but one *could* add their own custom screen function to the screen list when they program it, or you can daisy chain mpguinos as much as you want with a simple "y" adapter:




5. I know, mentioned above. I am thinking about it a little bit, but not very deeply yet.


6. Tank or current resets? Current will reset after 7 minutes of inactivity. If tank is resetting occasionally when you use the starter then you need a better power connection to your battery, maybe run your power leads straight to the battery terminals and see if that helps.


PS: The injector high time and vss count is accumulated in an instance of Trip named "tmpTrip". To fix number three, (once I have my own timer ISR), we need to keep track of the time between vss pulses and compute the speed from there rather than from the number of pulses recieved in the last 1/2 second. I need to debounce the vss pulses properly first though so the metro doesn't need such a hacked vssPulsesPerMile figure (again dependant on the fancy schmancy timer ISR). Why don't I just quit messing around and do that?
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Last edited by dcb; 07-25-2008 at 08:50 AM..
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Old 07-30-2008, 07:13 PM   #4 (permalink)
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Quote:
Originally Posted by dcb View Post
...I need to debounce the vss pulses properly...
The Starion needs a debounced VSS. The signal comes from a reed switch mounted at the speedometer and it's very noisy...

Last edited by starquestPilot; 08-01-2008 at 09:22 AM..
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Old 08-01-2008, 08:00 AM   #5 (permalink)
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Just FYI, I'm making some progress on the timer/event stuff. I did a test in the metro with a software debounce (schedule the interrupt re-enable 5ms later) but I still had to double the vsspulses/mile and the o-scope is still broken. I do have an ISR though and will probably disable timer0 and make my own millis(), delay(), etc() because I don't want to compete with timer0 for the CPUs attention.

Cut and paste code is nice, but I have to fight with arduino sometimes. If the arduino IDE takes over the timer2 ISR I will have to say it isn't worth it and drop into AVR and figure it out from there.

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